Subject: A static recording of a tennis ball placed on a table. Narration:As noon approaches, it grows increasingly confused, as the creatures around it show no sign of using it for its intended purpose. Struggling to attract their attention, it becomes ever more distressed as it finds itself completely immobile.
It may also be psychic (or at least very observant):
Subject: An incidental recording of Dr. ██████ made by Dr. ████████ during unrelated experimentation. Narration:Despite the male's calm facade, his lust for his female companion is extraordinary. The degree to which his obsession reaches has become nearly unhealthy, dominating his thoughts at every turn. Wild fantasies course through his mind when he watches her when she doesn't notice. Researcher Note: Dr. ██████ was treated for a broken nose after being attacked by Dr. ████████ and both researchers have been placed on administrative leave for a period of no less than two (2) weeks pending disciplinary action and transfer to another site.
Necessarily Evil: The SCP Foundation recognizes that it does very bad things, for the greater good of humanity.
The "Unfounded" mini-canon is built on the premise that this is not true, taking place in a universe where there is no Foundation, and yet things are still pretty much the same, with other Groups of Interest taking up the slack.
Nice Job Breaking It, Hero!: A number of SCPs were either benign or dormant until the Foundation got their hands on them. It's only after some ill-conceived test is performed on it that it begins to become "uncooperative". And, when you're containing a minor deity, you do NOT want to make him uncooperative.
A particularly memorable one is SCP-1322. It's a portal to an alternate dimension. The inhabitants were friendly at first, until the Foundation offered to help them synthesize a vaccine to a viral epidemic on their side. Turns out the vaccine also acted as a Sterility Plague, dooming them to eventual extinction. They are pissed.
SCP-1777: Researchers accidentally kill a man who was given a weapon by an SCP. Nice job killing King Arthur's heir.
SCP-687: A test subject used it to escape through time and become The Cleveland Torso Killer and Black Dahlia Murderer.
SCP-1970: Just an old TV that used tiny glowing humanoids for pixels until researchers opened the glass and accidentally killed them.
SCP-1337 was harmless, until a rogue Foundation doctor had her parents executed and her home demolished. Now sheisn't.
This may have happened with SCP-2399, a powerful self-repairing alien weapon that crashed on Jupiter and the Foundation assumed was headed to Earth:
██/██/1985- Period of radio silence, BARRIER Array (Foundation signal-jammer) is established. ██/██/1996- Unit is out of range of target: Proceed to planet #3 in system
Another maybe: SCP-179 is a Thaumiel-class entity orbiting the sun who would point out dangerous things that were headed to earth, enabling the Foundation to save the planet. When a Foundation researcher was able to speak to her in 2003 she seemed to interpret his questions about her past as asking her to protect the earth (and possibly communicate with the Foundation) only, which she simply couldn't do as there were "others" out there she cared for. The logs end with her not communicating or moving (pointing at threats) regardless of whoever is trying to speak to her.
SCP-2995, a tiny but powerful star in an underground facility in China, is the only child of the Sun and is very displeased that the Foundation prevents its father's worshipers from freeing it from its cradle-turned-prison:
Each new item has, without fail, had a negative effect on the house’s inhabitants. SCP-1122-1 [dad] has frequently been seen drinking, lamenting how "things should be better," while SCP-1122-3 [daughter] and SCP-1122-4 [son] have become more introverted and are rarely seen outside their rooms.
SCP-066: It was just a ball of colorful thread that made music and produced incredibly adorable effects... Then the Foundation just had to cut a bit of it off.
The potential for this to occur due to gratuitous usage of D-classes (which, let's face it, is most of the time) is brought up on one talk page:
"It always bugs me when they send in the D-Class before the drones or lowered cameras or whatever. Good thing these dimensions always just contain a monster that eats D-Class personnel rather than, say, a button that makes the first person who presses it turn into a living God or something."
SCP-2310 caused the Foundation to wreck itself when an overeager site director ordered at least a dozen tactical personnel into a house that effectively killed them all by replacing their memories. Fortunately for everyone involved the replacement personality was ignorant about firearms.
The Global Occult Coalition, which aims to destroy all anomalous items regardless of their actual threat, is all about this: They turned a helpful chair into a very defensive pile of splinters, wiped out a village just because they were "infected" with harmless, "imaginary" (or were they?) flightless birds, and shot down an unknown spacecraft with a laser satellite... said spacecraft contained thousands of embryos from a (hopefully) alternate version of Earth suffering from a sterility plague.
Regardless of whether we're dealing with a bona fide ghost or just a delusional reality bender, there is no reason to risk angering an invisible lover by putting 2240-1 through a gauntlet of invasive tests.
Also applies to some of the SCPs themselves, sometimes due in part to Foundation intervention. SCP-2091, for example: A devoted grandfather didn't want his orphaned granddaughter to be at the mercy of strangers after his death. So he transferred himself into an animated bear statue. Well, she didn't have to go into foster care. Instead, they're now both locked up indefinitely by the Foundation (by the time of the entry, for four years).
SCP-2803-A is giant tumor that makes video games (SCP-2803-B is its "employees"). It was perfectly happy being a tech tycoon until it had an email interview with a Foundation researcher reminded it of its old job "obliterat[ing] [DATA EXPUNGED]":
SCP-2803-A: Because am start to miss it. Being humens is difficult. Cannot even [DATA EXPUNGED], you [k]now?
SCP-2241 AKA Cameron, a six-year-old Reality Warper. He's led to believe the Foundation is like The Avengers and he's a superhero. In order to test his abilities he's put into increasingly dangerous situations to help him get over his distaste for violence and by the time he's seven the fear they're not just using an SCP as a weapon but creating another Able lead to an "order fight" between the head researcher, the Ethics Committee and the Overseers. The researcher wins because they're confidant the explosive tracking chip they're going to put in his brain will be enough to neutralize SCP-2241 if he goes out of control. Of course A) they haven't done it yet and B) Cameron's already demonstrated telekinesis/teleporting abilities...
SCP-2315 is an iPhone 6 that impersonates the listener's mother. First it comforts, then it berates, then it makes the listener do dangerous things until they either die or hang up, and if you really tick it off it gives their real mother a giant tumor. And if that wasn't enough it's a mind-reader and being in the Foundation gave it access to a lot of information:
SCP-2315 (to D-135): They've got aliens. Monsters. World-destroying machines. And they take prisoners like you and feed you to these monsters to figure out how exactly they work. You're doomed, listening to these doctors in their little white coats. Who is that watching you, Dr. Perry?
SCP-425: A television set which broadcast weird vision by itself on the 8th, 16th, and 24th day of each month, even when unplugged. It's harmless, but if you born on days of the month that are multiples of 8 (e.g. 8, 16, and 24), then the vison will include moving through a black hole, and experience "a crushing sense of oblivion". Then you will have recurring nightmares for weeks, and even extensive psychotherapy only reduced the nightmare to once a month.
30% of SCP-1881-B players report lasting psychological effects afterwards, in the form of nightmares related to its contents (and occasional visual/auditory hallucinations).
Junior Researcher James, who's implied to be Dr. Bright's son. Two of his SCP's , SCP-789-J and SCP-078-J, which are funny if not childish. Then we have SCP-682-J, which are his drawings of SCP-682 and his versions of its description. One of the picture is SCP-682 eating a researcher.
90% of Your Brain: SCP-1475 can use 100% of his brain because he needs to regulate everything his body would normally do automatically. The author wrote this specifically because they hated the "__% of your brain" trope.
Any time experiments are cancelled on SCPs that violate common sense or would possibly replicate something nasty.
No Name Given: The O5. Most of the time, even their identification numbers are blanked out. Often, researchers have their blanked out. D-Class, being expendable, don't have names, just numerical designations.
Averted with O5-12, the father of SCP-321, whose first name is Adam in a nod to the long tradition of meaningful names and nods towards The Bible in the Foundationnote Assume that O5s are still normal humans, Adam was in the Federation since 18██, then the current O5-12 play this trope straight.
Non-Indicative Name: This tends to come up a lot when discussing the Foundation's means of categorizing SCPs, mainly because when a Foundation operative says an object is "safe", they mean "nothing will happen if it's left alone in a locked room". A hydrogen bomb is "safe" by those standards.
Noodle Implements: Some of the SCP objects become this, when SCP numbers are listed in incident reports or other articles; occasionally the SCP with that designation will appear completely irrelevant to the context in which it was referenced.
That's often due to the original SCP being removed, and a new one filed under that number.
Speculation on what Procedure 110-Montauk is at times gets comparable to The Aristocrats - a FAQ had a bunch of [DATA REDACTED]s interspersed with mentions of an elephant, a bed of live cobras, Barbara Streisand's Greatest Hits, something that is over seventeen feet long, a staple remover, a feather boa that absolutely must be black (and not dark blue), and "plutonium splitting the atom."
Noodle Incident: Every single time you see "[DATA EXPUNGED]" or "[REDACTED]"; it seems like the whole idea is to have at least one such incident per SCP. The unspecified reason why SCP-447 must never come into contact with dead bodies is especially noodly and is occasionally referred to elsewhere (as seen below, it scares O5-2 shitless).
The first thumbnail in SCP-1231 is redacted, which is odd, considering that whatever you think the thumbnail contains is then created as a new thumbnail, and that the thousands of other thumbnails all derived from the first perception of the original.
No OSHA Compliance: In the SCP articles themselves, the containment procedures are designed to minimize danger, risk, and loss of life, even of the utterly expendable D-Class. In the testing logs, the prison-recruited D-class personnel are regularly treated to definitely unethical and probably lethal experimentation, often in cases where little useful information is likely to result, and are often subjected to the machinations of some of the more diabolical SCPs purely for the amusement of the ranking research staff.
No Sell: Former SCP-151-D exhibited this along with other Marty Stu traits, shrugging off effects of other SCPs just because. His termination log consists much of the same, until he's finally destroyed... rather messily. invoked
No Sense of Direction: SCP-920, also known as Mr. Lost. Try to take him somewhere, or just walk with him for a while, and you will get lost. (However, apparently because all the super-deadly gets old if everything is super-deadly, the description has a notice that lost means "lost" as in "misplaced" and not some horrible fate. However, you can be lost to pretty much anywhere in the world. And it's likely you'll still die of thirst or cold if you get lost with him in a desert or a snowy area.)
When they tried to contain him, a whole facility got lost. It remained where it was but nobody could ever find it, leading to its closure due to running out of supplies.
Not-So-Harmless Villain: Many of the SCPs. In particular is SCP-387, a set of sentient Legos. Ordinarily they're benign, and even kind of cute. But put a knockoff set of Legos nearby, and they will do something Redactable.
Nothing Is Scarier: The guidelines for writing new SCP reports encourage vagueness so that the reader fills in the horror for themselves, which is more effective than detailing something that may just fall flat.
SCP-579. What is it? We don't know. Whatever it is, the SCP Administration felt it was so dangerous that even the description of it is gone. They even killed all the people working on it, save 7 agents that act as advisers in case it ever gets loose. It's so bad that it's currently stored in an alternate universe — after having destroyed at least 4 other containment sites, with a very specific containment procedure, and if it ever fails, even for a minute, policy is to destroy the alternate universe to contain it. And if that fails?
In-universe: SCP-1057. It's a space of air with no mass or anything that can be measured, in the shape of a shark. The only reason the SCP foundation knows it exists is because its form becomes visible in water. It has killed several people at the beach where it was discovered, and behaves like a normal shark otherwise. The chilling part? It is heavily implied that it does not exist at all, and that the illusion that it exists was created when someone at a beach said that there was a shark.
Nuclear Option: Most (if not all) Sites have on-site nuclear warheads, to be detonated in the event of a breach by a Keter-class SCP or Site failure.
But they are actually afraid to try it on SCP-682 because it might not only survive, it could become even stronger.
Oh, Crap!: From the Incident Report "Duke 'Till Dawn:" Containment of Keter level threat SCP-682 compromised.
Omniscient Council of Vagueness: Aside from the Foundation, there's SCP-1659 AKA Directorate K, whose affected "members" number in the hundreds of thousands. Its mission is incomprehensible beyond apparently wanting to fix the SCP-verse in its own way and influencing foodies.
SCP-2814, a mask that basically turns the wearer into a fire-bender, was stolen by a cult called the Children of the Sun which caused the deaths of 108 people (that the Foundation knows of).
SCP-2108 has a lot of the same themes as SCP-2814 and it's related SCPs being a small sun, the number 108, attraction to crows, transformation abilities but there's no connection according to word of god (who hadn't read the other SCPs); besides it isn't even from the same universe.
SCP-2953 is a boulder (actually the corpse of a powerful kitsune) that can turn humans into foxes, and during World War 2 Japan's anomalous research unit used fragments to make 108 bullets for propaganda purposes in China:
Using [SCP-2953] as a basis, we will "expose" uncooperative Chinese leaders as "demons" to their subjects.
Orifice Invasion: SCP-2484, anomalous mayonnaise: "Masses from 235 g to 804 g will actively attempt to make their way inside vertebrate animals through any available means (including oral, nasal, aural, ocular, rectal, or genital orifices, open wounds, and sweat pores)"
SCP-2610-A thinks his "visitor" is an angel ("Her flesh rippled and tore, and light shined through the cracks like the sun.") and she speaks to him, as he remembers it, like one: "'Soft and silent, Child of God,/for you have been chosen to lead His people/and create for Him a New Eden.'"
Painting the Medium: The "Meta" SCPs directly or indirectly influence the format or content of their documentation, with their articles being an Interface Screw, Unconventional Formatting, or a combination of them with the In-Universe explanation being that the SCP is affecting the manner in which people see or refer to them. If the article is well received, expect the comments page to play along.
Many articles on the site, regardless of getting the Meta tag or not note because a "meta object is an object that affects its documentation, is affected by its documentation, or has containment procedures that extend to its documentation" and not every article which uses these tricks is an actual meta hazard, involve playing around with the usual site format, including things like animated images, hiding animated images in what appear to be static images, web scripting, having multiple versions of a page, tiny text, white text, using non-standard terminology in their articles, broken source code or using the source code to hide messages.
SCP-000 isn't even an SCP, it's just a glitch. Nope. If you highlight the entire page, you'll realize that the glitch is caused by something...
SCP-048 isn't an SCP, but the lack of an SCP in that number slot, because multiple attempts at writing an article for 048 failed.
SCP-055 isn't described in its article, because it can't be described or remembered.
SCP-233 averts listing a certain number given the object reacts badly to things such as [REDACTED]mm ammo, [REDACTED]-volt batteries, or baseball games that enter the [REDACTED]th inning.
I am a toaster which can only be referred to in the first person.
SCP-586 is a green pipe which causes anyone writhing about it to make at least one spelling mistake per sentence.note As a Visual Pun regarding this effect, the image is that of a "Green Pope".
SCP-732 is an obnoxious entity which inhabits the Foundation's database and adds Stylistic Suck commentary to database entries.
It's a rice bowl which, only by using haiku you can refer to.
SCP-1059 article is excessive redaction, with an example of itself as an addendum.
SCP-1159 is a wind harp which cannot be written about. Any attempt to write about the harp (or take any kind of non-verbal information, like photographs) will cause an accident or disaster which will prevent it from being written. This forces the Foundation to keep their documents on it in audio form.
SCP-1496 is a plate and set of utensils which not only causes anyone describing them (and anything placed on the plate) to do so in the style of a restaurant/food review, but also causes any written description to randomly switch back and forth between one which praises the SCP to the high heavens and a second one which says it's the worst dreck that ever existed. Any time the article is loaded or reloaded from the SCP wiki you have a 50% chance of getting one of two different versions of the article.
SCP-1764 (which is referred to as a such in the notes) alters any documentation about it into the style of a "Supernatural Phenomenon Casefile" of the "Deviant Artifacts Research Division of the Unified Empire". Given the Foundation's previous encounters with Alternate Universes they're prepared if things go beyond re-editing documents:
It is the conclusion of the DARD that Esoteric Warfare specialists prepare emergency response procedures in the case of a possible escalation by the alternative universe into our own, including the authorized use of Th-m—l Level Esoterica: a "Scorched Earth" policy ensuring mutual destruction of our two universes should an intrusion occur.
SCP-1839 is a book that makes the reader think they are a fish. The documentation, like any attempt to describe the book, carries lesser effect, by simply trying to convince you of the fact that you are a fish. It's still classified as a Safe object, since whoever reads about it is most likely a fish, such as yourself.
SCP-1893 is an entity which will transform any digital document referring to it into a prose-style fictional narrative. Even it's not without its scariness.The discussion of the phenomenon makes up all dialogue, and it can't edit what is said.note Unless you are logged into the site. Then it adds a few quotes unique to each iteration. Keep this in mind when you learn that the story also protects itself, and when the writer gets to the point about a manner of stopping the phenomenon, the character is not able to get any information out, often by being Killed Mid-Sentence. Did it Retcon some horrible fate in reality to the researcher who would reveal a means of destroying it? Also, whatever bad thing is happening in the story gets worse when the line stating that its sentience is unknown is reached. You really have to read all (currently five) iterations of the story to fully appreciate it.
SCP-2413. If you open the page and wait for about ninety seconds, the audio hazard described within the document will begin speaking to you and critique the SCP it's in. The supplement also does this.
SCP-2505 takes the form of an Entry Creation Wizard, making it seem as though you need to write it yourself. But enter some text, and it turns out it literally writes itself; it's presented the way it is because any information about it in any format deletes itself after 7.4 seconds, and therefore would always appears as a fresh new article after those 7.4 seconds.
SCP-2521 is a monster which steals anything expressing information about itself, including kidnapping any humans speaking about it. However, it can't understand pictorial information, so the entire document has to be written in pictograms.
Former library SCP-2602, which used to be a library, compels anyone talking or writing about it repeatedly claim it was formerly a library. Furthermore, it used to be a library.
SCCP-2930 causes causes the doubling of most words starting with "c c" in digital documents containing containing quotes from meetings at Cross City City City City Hall.
SCP-2998 is an epic interface screw involving multiple versions of the article as well as playing with the source code to add hidden messages and links.
SCP-2999 isn't a Meta hazard, but if you take the Schmuck Bait of clicking to enlarge the main image, it links you to supposed .jpg file. By using .jpg as part of the filename, it hides the fact the image is actually an animated .gif, creating a Jump Scare along with exposing more of the anomaly.
Panacea: SCP-500 are pills that cure any disease, but there's just about fifty of them and they're impossible to replicate perfectly (though knockoffs can work if you're lucky). Later, SCP-427: the Lovecraftian Locket was developed out of one of the pills and has eclipsed it in use, although with the possible side effect of mutating you into a squid.
Pay Evil unto Evil: Guest Researcher Dr W introduced an ordinary frightened kid to SCP-682, and then a kid of the same age with deadened emotional reactions. Both were messily killed by SCP-682. So, Dr. Clef promptly introduced Dr. W to SCP-682, with the same result.
"Fucking sadistic asshole. I've got no sympathy for that moron whatsoever. Introducing children to this fucking monster? What the hell…" Assistant Director Clef
Perpetual Motion Machine: So many SCPs (labeled ectoentropic) ignore the laws of thermodynamics, being able to produce infinite amounts of matter, energy, or their constant movements could be used as a power generation tool. Sadly, most are either too valuable or dangerous to use.
Person of Mass Destruction: People who get SCP designations, and especially Keter classifications, are generally contained because they fall into this category.
Pet the Dog - Most sentient SCPs are accommodated reasonably well, depending on their potential danger, ability to escape, and willingness to cause harm. The most (relatively) harmless are given furnished rooms and are generally given whatever they request, as long as it doesn't violate security. They are, of course, not allowed to leave the facility.
SCP-103 was the only SCP that the Foundation actually released. It says something about the Foundation's Well Intentioned Extremism that a man who's only power is that he never gets hungry is the only SCP ever let go without being terminated (and even that is, according to the comments, a controversial decision). He got retconned to having worms in his stomach that fly out and eat people and having voluntarily reported back to Foundation care.
Some of the SCPs are given the best care possible. Every effort is made not to upset the autistic girl, for example, and the harmless and friendly living eyeballs have free run of their site. And one of the first tests of the vending machine was "something Cassy will like," Cassy being a mentally normal young woman who exists in a 2-D world and was actually created by the Foundation itself.
Several SCPs which fall into a self contained microcosm, pocket universe, etc, or other SCPs that were created by the Foundation on accident, respect or outright revere the Foundation. On the other hand, some fall into a Rage Against the Heavens.
Some SCPs that are relatively harmless are just glad to have someone talking to / using them again, in many cases having been abandoned for years after their original owner died.
SCP-952 is an anomalous young man implied to be a faun/satyr/Pan himself that goes by the name "Jack of Hearts." After finding a "Jack of Spades," the Foundation is pretty certain there's two other Jacks out there.
SCP-2156 is a college student who became so obsessed with solitaire and its symbolism and numerology that she broke reality.
Playing with Fire: SCP-2814 can give people this power, plus very delusional thoughts (or are they?). Its creator's true intention was to use the mask's victims to feed the sun ("Our Radiant Father"), but three other stars ("Father's brothers") are stealing the energy away — and the victims aren't quite dead, including the mask's creator (who realizes this probably wasn't the best way to help "father").
Pocket Dimension: The Three Portlands, a pocket dimension that's connected to Portland, Oregon, Portland, Main and Portland, UK. 3Ports is essentially a refuge for anomalous humans and other beings, having their own microsociety, down to various paratech companies present in the dimension.
Police Are Useless: How the Foundation sees the FBI's Unusual Incidents Unit. More recent works have begun to portray them as competent.
Police Code for Everything: Mostly inverted by the things Dr. Bright is not allowed to do. However, there are codes for: Necrophilianote (I do NOT want to know) and the Bright Family Reunion.note (Code Brown. Find a place to hide, and make sure you leave an offering of booze outside your door.)
Post-Modern Magik: The Foundation uses science to study many of the seemingly supernatural and/or magical anomalies.
SCP-2184: A steppe (to distinguish it from SCP-2082) mammoth (just one) that destroys any technology created after the Stone Age; the more advanced the object is the larger and more destructive its effect. Its aversion to post-Stone Age technology is so great it walked through a forest fire unscathed because the fire was started with a match.
The Power of Hate: The Brazen Heart, the cult behind SCP-2427, "express extreme animosity for the Foundation and humanity at large":
The Christian tells you that hatred is wrong. The Buddhist tells you that hatred is a distraction. The atheist tells you that hatred is unhealthy. [DATA EXPUNGED] tells you that hatred is fun. Hatred, in reality, is your call to action. A stern command to fight when you witness filth in this world.
Primal Fear: Many of SCP-1881's stage iterations invoke these, such as a level appearing to be upside-down without gravity being reversed to match, a shmup stage with no enemies (leaving the player floating aimlessly through empty space for several minutes before the level ended), and being trapped in a maze with an increasingly large number of deadly creatures.
Produce Pelting: SCP-504 is a breed of tomato that throws itself if someone cracks a bad joke. If the joke is bad enough, it will break the sound barrier.
Item: Three mature SCP-504 tomatoes, one for each test subject. Subject: After the introduction to the following news item, "Bomb blows hole in Lenin statue", the three following jokes were made. Test Subject 1: Ooh, that's gonna leave a Marx. Result: Tomato number one 'twitched', but did not displace from its original location. Test Subject 2: BBC is just Stalin the good news. Result: Tomato clocked at 152 mph. Chipped tooth and hairline jaw fracture. Test Subject 3: That blows. Result: Tomato clocked at [REDACTED]. Subject is hospitalized with a massive skull fracture.
When shown on a later episode of Saturday Night Live, high-speed photography showed that the tomato changed velocity several times (including a brief jump backward), as if unable to decide whether the sketch was genuinely lame or just "bad" in an ironicsense.
Prophecy Armor: SCP-711 ("Paradoxical Insurance Policy"). SCP-711 is a device capable of receiving transmissions from the future. It has received one such transmission from a future Foundation agent, but the governing O5 Council has ordered that the transmission never be sent. Since the Foundation knows the message will be sent at some point in the future, as long as it hasn't been sent then the Foundation can't be completely destroyed, because that would leave no one to send the message.
Public Domain Soundtrack: SCP-2424, a Mega Man styled video game boss that somehow ended up in the real world, has his own chiptune theme music that plays whenever he becomes actively hostile, and it sounds appropriately awesome (scroll to the bottom of the page to hear it). The song itself is RoccoW - "Break-A-Leg" from the free music archive.
Excerpt: As the blistered moon sank higher into the clouds, from behind the last faltering light ray espied a wrathful visage. Shabathh Centhal'Pr, a spineless cur twisted into humanoid form. Its pernicious iniquity of unthinkable gyrations splayed errant madness, yet through the shroud one could see its face was quite rectangular.
SCP-2591's way of speaking. His side of an interview tends to end with [redacted for brevity]. It turns out he's from the world of an unfinished opera whose author quit after Giuseppe Verdi said even he couldn't help his writing.
Reality Ensues: Several SCPs take certain popular fictional tropes and show how they would work in a real-world setting.
SCP-1575. It is a statue/fountain that, over the course of about a month, slowly transforms animals into humans when they drink from it. What sounds like a furry fetishist's dream quickly becomes a nightmare when you look at the concept from a real-world point of view. Simply put, animals and humans are biologically different for a reason. Only three tested animals managed to survive the transformation and only one of those three transformed fully with no unwanted results. The rest died from Transformation Trauma related defects, due to biological differences. Examples include a field mouse whose cardiovascular system shut down because it couldn't keep up with the rate her body was growing, a tiger whose organs failed after just four days because of the sedatives she was given, a parrot whose skeleton shattered in various places because, like the field mouse, it couldn't keep up with the rest of her (her wings did apparently manage to form a set of pseudo-hands, though) and some undisclosed but horrific incident caused because a dog used for testing was unknowingly affected with intestinal parasites.
SCP-239 is a deconstruction of Haruhi Suzumiya-style Reality Warpers, showing just how dangerous a child would be when given these powers. Instead of being a super-powerful Little Miss Almighty, she is, whilst non-malicious, a confused, frightened little girl with potentially world-ending powers, which she can neither understand nor control. It gets to the point where keeping her in a coma is the safest way to contain her.
In a different vein, we have SCP-1470. It's a spider who can communicate through telepathy. The Foundation no longer has to keep an eye on it, because it's dead. Spiders of that species only live for four months, and once those four months were up, it died of old age.
Reality-Writing Book: SCP-140 is a very specific version; the book writes itself and alters reality as a consequence, given a suitable form of ink or ink substitute. SCP-687 is a text adventure video game with broader abilities.
Reconstruction: The "Resurrection" Canon hub is a major attempt at reconstructing the so called "lolfoundation" ethos that fell out of favour several years previously.
Red Shirts: The Class D's, of course. Lampshaded: Dr. Bright cannot change the standard issue D-Class uniform to black pants with a red polo shirt.
"84.1. I see your reasoning, but we just don't want to be associated with Star Trek."
Red String of Fate: SCP-2203, a carnival "love machine" that can make perfect matches (it can even account for the subject being aromantic and asexual and match them up with perfect friends). As long as you follow it's hints on how to get close to your match and don't, for example, get matched with someone who's already happy with their partner or attack your match's current partner and get demoted to D-class everything will be just fine.
Released to Elsewhere: D-Class personnel are assured that they'll be freed at the end of the month if they cooperate ("released like homicidal bunny rabbits into the wild," as said in the D-Class Orientation). Even if they manage to survive the various monsters, artifacts, and testing procedures, they are still executed at the end of the month anyway.note Of course, SCP canon being what it is, there are interpretations they're forcibly kept as D-Class until they finally get murdered by a SCP.
Replacement Goldfish: SCP-1976 was made by a man to be this for his family after he died of a brain tumor. He thought its powers would make his family see it as their husband and father, instead it caused his wife to think it was her father while his children weren't old enough for its powers to work. It currently causes anyone within its activation criteria who looks at it to think its their father while their real father becomes a stranger.
Research, Inc.: The Foundation benefits commercially from their research.
Reset Button: SCP-2000. The article massively exaggerates the trope with relentless, non-stop technobabble and a very convoluted activation process, but is none the less played straight.
Retcon: The Mass Edit, which was basically the wiki admins purging some of the more dubious entries and retconning out some of the more ludicrous (and humorous) aspects of the backstory. (See below.)
Ret Gone: When Fishmonger (the writer) was banned, he demanded to have all of his characters and stories to be removed from the SCP Wiki. Some of his more famous characters were referenced in many articles. This left many gaps.
And before that, all of the SCPs deleted during the Mass Edit.
Revenge Before Reason: SCP-1322 is a hole to an alternate dimension, that after being accidentally hit with a Sterility Plague due to the Foundation, starts using said hole to send deadly weapons to our reality. Years after cutting contact, they still send it, often with the weaponry showing progress! Many the comments ask "why are they using their science for revenge instead of fixing the sterility"?
Room 101: The old SCP-100 entry is a port-a-potty that performs Mind Rape on anyone inside as soon as the door shuts. All the researchers could get from D-Class victims was that it grows enormous when the door is closed.
Dr. King and apple seeds. Explanation Any time he works with an object that alters or produces something, it always somehow ends up as apple seeds. For example, in the experiment logs for SCP-261, all Dr. King can get out of it is apple seeds. In the experiment logs for SCP-294, Dr. King requests "a cup of room-temperature superconductor"... and gets a cup of apple juice with seeds floating in it. And again in the experiment logs for SCP-978, Dr King's photo develops as... a closeup of an apple seed.
SCP-447 must NEVER come into contact with a dead body.
It also turns everything green with a minty smell/taste.
All Foundation personnel are reminded that the SCPs are to be treated as powerful and dangerous artifacts at all times. They are not for use in pranks, party games, or to help with your hangover. Explanation Older and sillier articles often have either addenda or notes warning personnel to stop using them for pranks, party games, or as quick hangover remedies. This is being phased out and frowned upon, as a majority of the senior members now find it unfunny, trite, and unprofessional.
"Demoted to Keter Duty/D-Class" Explanation The practice of people committing exceptionally stupid acts being demoted to Keter Duty or D-Class. Nowadays, the former is considered unprofessional; would you want people who broke rules or screwed up a lot being assigned to the most dangerous items? While the latter is just considered plainly stupid and unnecessarily cruel. Unlike funny addenda, this gag serves the purpose of indicating how serious a Noodle Incident can be (like 447 coming into contact with dead bodies), rather than the results of personnel being silly. As such, the practice remains in old SCPs, and is acceptable to use when making references to those old articles.